Metallic alloy for bearings

ABSTRACT

METALLIC ALLOY OF THE ZN-AL-CU TYPE, IN PARTICULAR FOR THE MANUFACTURE OF BEARINGS, COMPRISING 2-8% OF ELECTROLYTIC COPPER, 12-42% OF PURE ALUMINUM, THE REMAINDER ZINC WITH A HIGH DEGREE OF PURITY, AND INCLUDING AN ADDITION OF COBALT IN THE RANGE OF 0.02 TO 0.35%.

United States Patent O 3,667,941 METALLIC ALLOY FOR BEARINGS Aldo Dacco, Milan, Italy, assignor to Liasa del Dott. Aldo Dacco, Milan, Italy No Drawing. Filed Nov. 3, 1969, Ser. No. 873,506 Claims priority, application Italy, Nov. 14, 1968, 23,736/ 68 Int. Cl. C22c 17/00 U.S. Cl. 75-178 AC 5 Claims ABSTRACT OF THE DISCLOSURE Metallic alloy of the Zn-Al-Cu type, in particular for the manufacture of bearings, comprising 2-8% of electrolytic copper, 12-42% of pure aluminum, the remainder zinc with a high degree of purity, and including an addition of cobalt in the range of 0.02 to 0.35%.

BACKGROUND OF THE INVENTION Field of the invention It is known that in the manufacture of bearings use is widely made at the present time of alloys of copper and special bronzes. These bronzes have technical characteristics, such as good tensile strength, high resistance to heat, good elongation, optimum sliding characteristics, which, in their range of application, make them particularly suitable and almost irreplaceable as alloys for the manufacture of bearings.

Description of the prior art In view, however, of the fluctuating cost of copper and, within certain limits, also of tin, the prices being high in any case, which gives rise to a high cost of these bronzes, many attempts have already been made for some years past, and particularly during the second world war, to replace the bronzes by other alloys. From 1936, the applicant began the study, and then the production on a large scale, of alloys of zinc, aluminum and copper, containing a low percentage of copper, which had proved most suitable for use for bearings. The best behaviour was obtained with alloys containing the following percentages:

from 2 to 8% of Cu from 12 to 42% of Al the remainder consisting of Zn,

but these were still a long way from the highly favourable characteristics of the bronzes.

The Zn-Al-Cu alloys have, however, been the subject of continuous research aiming at the improvement of the respective characteristics, Italian Patent No. 5 17,577, for example, proposes to vary the ratio of the metals substantially, increasing the aluminum to 30-60% and the copper to Thereafter, Zn-Al-Cu alloys with a lower aluminum content came to be preferred again, from which it was evident that the percentage of aluminum could not be regarded as decisive, but was only a question of preference. In other cases, the addition of small percentages of supplementary materials, such as Sn, Mg, Be, Si, Sb, Ni, Cr, was also suggested for improving the sliding characteristics of the alloy. Notwithstanding the improvements, these alloys, even with their distinctly lower cost, have never succeeded in eifectively replacing the bronzes.

SUMMARY OF THE INVENTION The object of the present invention is precisely a further improvement in Zn-Al-Cu alloy, which is characterised essentially in that it contains an addition of cobalt, in a 3,667,941 Patented June 6, 1972 ice DESCRIPTION OF THE PREFERRED EMBODIMENT Following long and meticulous test made by the applicant, it has been found, in fact, that the stability of the alloy and the persistence of its technical characteristics, even at high temperature, are obtained all the more easily the purer the constituents of the alloy. It has been found that the purity of the zinc, which should not be less than 99.99%, is particularly determinative. Under these conditions, the addition of Co displays two precise functions: on the one hand, it substantially improves the sliding characteristics; it is meant to indicate by this term the ability of the alloy to retain a film of lubricant on its surface, even in the event of an interruption in the supply of lubricant.

On the other hand, it specificaly improves the capacity, or better the aptitude, of the alloy for withstanding heavy loads and wear, and in particular high working temperatures.

Before manufacture of the finished product, the alloy according to the invention may undergo known thermal stabilizing treatments, such as annealing at temperatures of the order of 360-390 C., for periods of 10 to 15 hours, this being possibly followed by a tempering treatment at temperatures between 220 and 250 C. for periods of 6 to 48 hours. In some cases, the annealing may be omitted and a simple stabilizing treatment carried out at 220-250 C. for period of from 6 to 48 hours. These thermal treatments are widely known, however, and may be varied within the limits of the skill of any good metallurgical expert.

I claim:

1. A metallic bearing alloy consisting of 0.02 to 0.35% cobalt, 2-8% electrolytic copper, 12-42% pure aluminium, and the remainder zinc with a high degree of purity.

2. The alloy of claim 1, wherein the aluminum has a degree of purity of at least 99.75% and the zinc a degree of purity of at least 99.99%.

3. The alloy of claim 1 modified by heating at a temperature from about 360 to about 390 C. for a period of time from about 10 to about 15 hours.

4. The alloy of claim 3 modified by a tempering at a temperature from about 220 to about 250 C. for a period of time from about 6 to about 48 hours.

5. The alloy of claim 1 modified by a heating at a temperature from about 220 to about 250 C. for a period of time from about 6 to about 48 hours.

References Cited UNITED STATES PATENTS 1,663,215 3/1928 Peirce et al -178 AM 1,767,011 6/1930 Pack 75-178 AC 2,900,288 8/1959 Pelzel 75178 AC 3,031,298 4/1962 Derntl 75178 AT 1,506,772 9/ 1924 Pack 75178 R FOREIGN PATENTS 362,507 12/1931 Great Britain 75l78 AC L. DEWAYNE RUTLEDGE, Primary Examiner E. L. WEISE, Assistant Examiner US. Cl. X.R. 14832 

